21 May, 2023

EA8/LA3ZA April 2023

This was a fun holiday operation from the island of Tenerife with 2.5 - 4 Watts running digital modes, mostly FT8 and some FT4 using a low-band and a high-band QDX.

The best bands were 30 m (29%) and in particular 10 m (65%) with a lot of contacts across the Atlantic ocean as the picture shows. In total 62 different entities/countries were contacted. 

QSL via Logbook of the World.

28 April, 2023

3 tips for not blowing the finals of the QDX transceiver

I have now used both the low- and the high-band QDXes daily as EA8/LA3ZA for a period of two weeks without destroying the four BS170 final transistors. Here are some procedures and tips.

But first, I do actually have experience in blowing the finals. That happended under testing prior to leaving, and all it took was 9.5 Volts for my 9 V build and what I thought was a dummy load, but which might have been an open circuit load. One BS170 developed a short between drain and gate with the result that 9.5 Volts was passed directly into the outputs of the driver IC5, 74ACT08, so IC5 blew as well.

My three tips for avoiding such failures are:

18 April, 2023

Clock cycles through chemical elements

The latest addition to the Multi-face GPS Clock is a clock face that for hour, minute, and second cycles through the corresponding chemical element in the periodic table. This is shown in the image to the right.

This is screen number 39 for this clock, all of them selectable by rotating a rotary encoder. The project, with Arduino Mega hardware and software is documented on Github, where the current release is v.1.6.0 (2023-04-14).

The display also shows  the full name for the element corresponding to the second, as shown above for element 3 which is Lithium. It is located in group (column) 1 and period (row) 2.

18 February, 2023

QDX Twins 80-10 m

My QDX twins from QRPLabs: 

  1. On top, the high-band version, 20-10 m, with a revision 4 PCB
  2. In the bottom, the original 80-20 m version with a revision 3a PCB
Both have been assembled for 9 Volts operation nominally.

My wife and I have identical twins in real life and at times one of the ways to distinguish between them was by different colors. Here it is the same, so the high-band QDX has a yellow LED and the low-band one has a green LED.

10 January, 2023

Audio delay - the unspecified parameter for ham radio transceivers

Elecraft K3: Upper trace is start of sidetone and
lower trace is start of RF ~15 ms later.
An amateur radio transceiver is not a precision measurement device. This is apparent when it comes to measuring time for your own round-the-world signal or when characterizing Long-Delayed Echos (LDE). One cannot just substitute onset of sidetone for the actual start of transmission of RF. Similarly there may be an unspecified delay between received RF and start of audio output on the receiver side.  

The main specification for ham radio transceivers is that the sidetone is synchronized with the keying. The delay to start of RF is only of secondary importance. All numbers should therefore be judged against the length of a dot which for instance at a morse code speed of 30 WPM is 40 ms. 

Here are some measurements for the Elecraft K3 and K2 that I did in 2021 for a presentation on LDEs at the HamSci 2021 conference. A video of the presentation is also available: Long delayed radio echoes – the illusive secret of the ionosphere

31 December, 2022

QDX with voltage regulator

Here's my low-band (80m - 20 m) 9 Volt QDX with a voltage regulator. Its only modification is a green rather than a red LED, as I don't like red LEDs to indicate anything but error conditions. 

The power amplifier of the QDX has hardly any built-in protection and can be ruined if run at full power into a poorly matched antenna. It will also easily be ruined if run at a higher voltage than the 9 or 12 Volts one may choose for at build-time.

20 November, 2022

W8BH clock with EU option

The TFT GPS clock with touch control which has been designed by Bruce E. Hall, W8BH, is a very nice clock with a large and easily readable 3.2" color display. Its three different screens have been nicely laid out and designed also. The processor is an STM32 Blue Pill.

I cloned the software and modified it in two simple ways:

1. EU option

This is a backwards compatible version which can be Europeanized with formats for date and units. It also has possibility for removing the display of the battery icon, when running from a USB supply.

New boolean variables to set:

  • US_UNITS - if false: m, kmh, Little-endian date with '.', if true: feet, mph, Middle-Endian date with '/'
  • BATTERY_DISPLAY - true: as original code, false: no display of battery icon and status

03 November, 2022

Planet positions for the Multi Face GPS Clock

Another update, this time to add:

  • Azimuth and elevation for inner and outer planets relative to your present location. The inner planet screen shows Venus and Mercury and alternates also every 10 seconds between showing the position of the sun and the moon. The % illumination is also shown along with an estimate of apparent magnitude
  • The combined local time and UTC display now has an option to show ISO week number, defined to start on Mondays. (It is my understanding that the week number in the US is different, as Sunday is the first day of the week)
  • A new calendar screen now shows Gregorian (western), Julian (eastern) as well as Islamic and Jewish dates. The calculation of the Jewish calendar is tough for the Arduino Mega and takes some 5-6 seconds
  • A screen showing GPS Info has also been included. This screen shows the number of satellites in view (line 0), the number of satellites in use for position fix and their average signal to noise ratio (line 1), the mode and status indicators (line 2), and the Horizontal Dilution of Precision, Hdop, and its characterization in plain text (line 3).